Field of the Invention
The present invention relates to an active vibration noise control apparatus for canceling out vibration noise based on road-induced vibrations with a canceling sound (vibration noise canceling sound), and more particularly to an active vibration noise control apparatus suitable for use on vehicles.
Description of the Related Art
While a vehicle is traveling, its road wheels vibrate as they roll on the road, and the vibrations are transmitted through the suspensions to the vehicle body, thereby generating vibration noise, i.e., road noise, in the passenger compartment. There has been proposed an active vibration noise control apparatus that cancels out such vibration noise with a vibration noise canceling sound which is in opposite phase with the vibration noise, at a sound receiving point (evaluation point) where a microphone is positioned (see Japanese Laid-Open Patent Publication No. 2009-045954, hereinafter referred to as JP2009-045954A).
According to the technology disclosed in JP2009-045954A, the active vibration noise control apparatus is constructed as a feedback active vibration noise control apparatus which operates as follows: In order to cancel out vibration noise as road noise having a fixed frequency, i.e., so-called drumming noise, at the sound receiving point, an error signal having the fixed frequency is extracted from error signals generated as signals representing an interference between vibration noise detected by the microphone and the vibration noise canceling sound, using an adaptive notch filter as a bandpass filter (BPF) for the fixed frequency. The extracted error signal is used as a control signal, which is adjusted in phase and gain, i.e. amplitude, to generate a corrected control signal. The corrected control signal is supplied to a speaker, which outputs a vibration noise canceling sound.